Third-party test data in tests/testthat/

The test suite carries data from two other projects, used as oracles. None
of it is in the installed package. The rest of zumime is under the MIT
licence (see LICENSE and inst/COPYRIGHTS).

1. helper-go-sniff.R

   The sniff cases of Go 1.27.1's src/net/http/sniff_test.go: each case's
   description, input bytes and expected Content-Type.
   https://github.com/golang/go/blob/go1.27.1/src/net/http/sniff_test.go
   Copyright 2011 The Go Authors. Distributed under the following licence,
   https://github.com/golang/go/blob/go1.27.1/LICENSE:

   Copyright 2009 The Go Authors.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are
   met:

      * Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
      * Redistributions in binary form must reproduce the above
   copyright notice, this list of conditions and the following disclaimer
   in the documentation and/or other materials provided with the
   distribution.
      * Neither the name of Google LLC nor the names of its
   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

2. helper-file-type.R

   The answers of file-type 22.2.0 (commit 11e0d64) on its fixture/
   directory: each fixture's file name and the MIME type file-type
   reported. tools/dump-file-type-answers, in the package repository,
   regenerates them.
   https://github.com/sindresorhus/file-type
   Distributed under the following licence:

   MIT License

   Copyright (c) Sindre Sorhus <sindresorhus@gmail.com>
   (https://sindresorhus.com)

   Permission is hereby granted, free of charge, to any person obtaining a
   copy of this software and associated documentation files (the
   "Software"), to deal in the Software without restriction, including
   without limitation the rights to use, copy, modify, merge, publish,
   distribute, sublicense, and/or sell copies of the Software, and to
   permit persons to whom the Software is furnished to do so, subject to
   the following conditions:

   The above copyright notice and this permission notice shall be included
   in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
   IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
   CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
   TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
   SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
